Using clinical cases of stroke models, one of the difficulties associated with evaluating the relationship between cortical damage/reorganization and functional deficit/recovery is the issue of variability. The patient population is heterogeneous with regard to both the amount and location of damaged cortical territory and, accordingly, the severity and type of physical impairment. This will also be true, albeit to a lesser extent, in non-human primate models of stroke. Project 4 proposes to use a focal lesion model of cortical reorganization, the specificity of which, will greatly aid our effort to reveal the fundamental principles of compensatory cortical plasticity. Specifically, our goal is to test specific hypotheses of cortical reorganization by ablating cortical regions that are important for motor control and by recording activity from those cortical regions that are likely to be compensatory during recovery of function. The relationship between plasticity and functional recovery are to be tested by combining focal lesions with targeted recording strategies, specific behavioral tasks, and readily quantifiable behavioral measures. The proposed experiments represents some of the earliest efforts to explore the relationship between cortical reorganization and recovery of function in this manner. In the short term, the specific approach will begin to unravel the complex relationships between damaged cortical territories, reorganizing cortical domains, and behavioral performance. In the long term, such knowledge should allow for more accurate prognoses and the design for rehabilitative strategies that are optimal for any given patter for cortical damage.